Animal Model Core B will provide all mice used in Projects 1, 2, and 3. The Core will be responsible for ordering mice, performing various manipulations required to induce experimental colitis, maintaining a specific pathogen-free barrier facility, performing roufine surveys, to ensure absence of pathogens in the colony, and assist in harvesting tissues from mice. Centralization of these functions in an Animal Model Core provides uniformity and quality control of mice being studied in the various projects, reduces cost, and will help conserve numbers of mice required by ensuring their optimal use in the projects. A second aim of the Animal Model Core is that of centralized pathologic analyses which will be performed by Dr. Trenton Schoeb, an expert veterinary pathologist. Tissue sections from the various projects are coded prior to interpretation and quantitative scoring where needed. This facilitates interactions among the projects and also the comparison of results between them. A third purpose of the Animal Model Core is to provide genetically modified transgenic and knockout mouse strains for use in experiments in the various projects. All of the above Aims have been accomplished in the previous cycle. In regard to the third Aim, during the previous cycle a number of novel genetically-modified mouse lines have been generated in Projects 1, 2, and 3 that have been extremely valuable in addressing innate and adaptive immunity to the microbiota, which is the central goal of this Program Project. These mouse lines include a CBirl flagellin T cell receptor transgenic mouse, an IL-10/Thy1.1 reporter mouse (lOBiT), an IL-17F/Thy1.1 reporter mouse, and an IFNy/Thyl.l reporter mouse. These mouse lines will be housed in Core B and made available to the different projects in this renewal application. Dr. Charies Elson will serve as Director and Dr. Casey Weaver will serve as Co- Director in this Core. Dr. Sam Cartner from the Department of Comparative Medicine will serve as Consultant. An Oversight Committee consisting of the PI of each Project plus Drs. Schoeb and Cartner will oversee the usage and function of the Core.